Operations Management

Transcription

1 13-1 MRP and ERP Operations Management William J. Stevenson 8 th edition 13-2 MRP and ERP CHAPTER 13 MRP and ERP McGraw-Hill/Irwin Operations Management, Eighth Edition, by William J. Stevenson Copyright 2005 by The McGraw-Hill Companies, Inc. All rights reserved MRP and ERP MRP Material requirements planning (MRP): Computer-based information system that translates master schedule requirements for end items into time-phased requirements for subassemblies, components, and raw materials.

2 13-4 MRP and ERP Independent and Dependent Demand Independent Demand A Dependent Demand B(4) C(2) D(2) E(1) D(3) F(2) Independent demand is uncertain. Dependent demand is certain MRP and ERP Dependant Demand Dependent demand: Demand for items that are subassemblies or component parts to be used in production of finished goods. Once the independent demand is known, the dependent demand can be determined MRP and ERP Dependent vs Independent Demand Figure 13.1 Demand Stable demand Demand Lumpy demand Time Time Amount on hand Safety stock Amount on hand Time Time

3 13-7 MRP and ERP Figure 13.2 MRP Inputs MRP Processing MRP Outputs Changes Master schedule Bill of materials MRP computer programs Primary reports Secondary reports Order releases Planned-order schedules Exception reports Planning reports Performancecontrol reports Inventory records Inventory transaction 13-8 MRP and ERP MPR Inputs Master Production Schedule Time-phased plan specifying timing and quantity of production for each end item. Material Requirement Planning Process Product Structure Tree Lead Times 13-9 MRP and ERP Master Schedule Master schedule: One of three primary inputs in MRP; states which end items are to be produced, when these are needed, and in what quantities. Cumulative lead time: The sum of the lead times that sequential phases of a process require, from ordering of parts or raw materials to completion of final assembly.

4 13-10 MRP and ERP Figure 13.4 Planning Horizon Assembly Subassembly Fabrication Procurement MRP and ERP Bill-of-Materials Bill of materials (BOM): One of the three primary inputs of MRP; a listing of all of the raw materials, parts, subassemblies, and assemblies needed to produce one unit of a product. Product structure tree: Visual depiction of the requirements in a bill of materials, where all components are listed by levels MRP and ERP Product Structure Tree Figure 13.5 Level 0 Chair 1 Leg Assembly Seat Back Assembly 2 Legs (2) Cross bar Side Rails (2) Cross bar Back Supports (3) 3

5 13-13 MRP and ERP Inventory Records One of the three primary inputs in MRP Includes information on the status of each item by time period Gross requirements Scheduled receipts Amount on hand Lead times Lot sizes And more MRP and ERP Figure 13.7 Assembly Time Chart Procurement of raw material D Fabrication of part E Procurement of raw material F Procurement of part C Subassembly A Final assembly and inspection Procurement of raw material I Procurement of part H Fabrication of part G Subassembly B MRP and ERP MRP Processing Gross requirements Schedule receipts Projected on hand Net requirements Planned-order receipts Planned-order releases

6 13-16 MRP and ERP MPR Processing Gross requirements Total expected demand Scheduled receipts Open orders scheduled to arrive Planned on hand Expected inventory on hand at the beginning of each time period MRP and ERP MPR Processing Net requirements Actual amount needed in each time period Planned-order receipts Quantity expected to received at the beginning of the period Offset by lead time Planned-order releases Planned amount to order in each time period MRP and ERP Updating the System Regenerative system Updates MRP records periodically Net-change system Updates MPR records continuously

7 13-19 MRP and ERP MRP Outputs Planned orders - schedule indicating the amount and timing of future orders. Order releases - Authorization for the execution of planned orders. Changes - revisions of due dates or order quantities, or cancellations of orders MRP and ERP MRP Secondary Reports Performance-control reports Planning reports Exception reports MRP and ERP Other Considerations Safety Stock Lot sizing Lot-for-lot ordering Economic order quantity Fixed-period ordering

8 13-22 MRP and ERP MRP in Services Food catering service End item => catered food Dependent demand => ingredients for each recipe, i.e. bill of materials Hotel renovation Activities and materials exploded into component parts for cost estimation and scheduling MRP and ERP Benefits of MRP Low levels of in-process inventories Ability to track material requirements Ability to evaluate capacity requirements Means of allocating production time MRP and ERP Requirements of MRP Computer and necessary software Accurate and up-to-date Master schedules Bills of materials Inventory records Integrity of data

9 13-25 MRP and ERP MRP II Expanded MRP with emphasis placed on integration Financial planning Marketing Engineering Purchasing Manufacturing MRP and ERP Figure MRP II Finance Market Demand Manufacturing Master production schedule Marketing Adjust production plan Production plan Rough-cut capacity planning MRP Capacity planning Yes No Requirements No Yes Problems? schedules Problems? Adjust master schedule MRP and ERP Capacity Planning Capacity requirements planning: The process of determining short-range capacity requirements. Load reports: Department or work center reports that compare known and expected future capacity requirements with projected capacity availability. Time fences: Series of time intervals during which order changes are allowed or restricted.

10 13-28 MRP and ERP Figure Capacity Planning Develop a tentative master production schedule Use MRP to simulate material requirements Convert material requirements to resource requirements Is shop capacity adequate? Yes Firm up a portion of the MPS No Revise tentative master production schedule No Can capacity be changed to meet requirements Change capacity Yes MRP and ERP ERP Enterprise resource planning (ERP): Next step in an evolution that began with MPR and evolved into MRPII Integration of financial, manufacturing, and human resources on a single computer system MRP and ERP ERP Strategy Considerations High initial cost High cost to maintain Future upgrades Training

11 13-31 MRP and ERP CHAPTER 13 Additional PowerPoint slides contributed by Geoff Willis, University of Central Oklahoma MRP and ERP Bill of Materials Part 1 A listing of all raw materials, parts, subassemblies, and assemblies needed to produce one unit Product structure Tree X Level 0 B(2) C 1 D(3) E E(2) F(2) MRP and ERP Bill of Materials Part 2 How many more of each component is needed to make 15 Xs if there are 5 of each already in stock? X B(2) C D(3) E E(2) F(2)